| The study area is located in the southeast of Sulige area in the northern Yishan slope of Ordos Basin.Based on geological logging data,scanning electron microscopy data,cast thin section data,mercury injection test data,physical property data,gas-water permeability data and core data,a geological database of the study area has been established,and the formation division and correlation of Majiagou Formation Ma51+2has been studied.Clarify the sedimentary facies characteristics,paleogeomorphology and reservoir characteristics;The characteristics of reservoir petrology,physical property,pore structure,gas and water distribution of Ma51+2reservoir are systematically studied,and a comprehensive reservoir evaluation is carried out to identify different reservoir types and to predict favorable blocks.The results showed that:（1）M51+2in the study area was divided into M51（M511,M512,M513,M514）and M52（M521,M522）,and mainly developed tidal flat subfacies,which were further divided into five microfacies:paste cloud flat,paste cloud flat,mud cloud flat,grey cloud flat and white cloud flat.（2）Karst highlands and karst slope palaeo-geomorphic units are developed in the study area,and drums,gentle slopes,depressions and gullies are further characterized.Reservoirs with high dissolution pores are developed in the gentle slopes and residual hills,and the reservoir space combinations are fracture-dissolution pore type,pore type and micro-pore type.The main pore filling assemblage is dolomite-siliceous（quartz）assemblage,dolomite-calcite assemblage and calcite-siliceous（quartz）assemblage.（3）The water type in the study area is Ca C12type,which has the characteristics of"deep metamorphism and high concentration",good sealing,which is conducive to gas accumulation.（4）The effective reservoirs in the study area are classⅠ,ClassⅡand classⅢ.Combined with the comprehensive evaluation of reservoirs,three favorable blocks are predicted in the study area,namely favorable area A,favorable area B and favorable area C. |
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